Identification of possible determinants of inequality in breast cancer survival that are amenable to interventions is an important concern, given the high incidence of the disease and its burden in Wisconsin and the U.S. A population-based study will help elucidate baseline hazards, cumulative hazards and excess risk variations by regions or among subpopulations, as well as possible determinants of that variation. This study will pursue this complex issue from a multi-disciplinary, multi- level approach. Therefore, it will focus on the relationships to breast cancer survival of community-level characteristics, individual socioeconomic status and proximal factors like behavior risks, indicators of access and quality of cancer care and tumor characteristics. This population health perspective will permit a more comprehensive understanding of the complex processes involved in differential survival and may facilitate insightful and creative interpretation of the findings. Data from the 14,000 cases and controls from the Women's Health Study, a population-based etiologic study conducted by Dr. Pony Newcomb at the UW-Comprehensive Cancer Center, will be used for this study.